4o6 SCIENCE PROGRESS 



direction may have an influence upon the growth and differenti- 

 ation of quite another part of the structure of an organism, 

 attention may be drawn to the dependence of the increase 

 of brain capacity in mammals upon the adoption of a hairy 

 covering consequent on the reduction and final abandonment 

 of scales. To this may be attributed the formation of the 

 neopallium, which G. Elliot Smith ^ explains by the fact that 

 " in the immediate ancestors of mammals the number and 

 variety of sensory paths which found admission into the cere- 

 brum became enormously increased, and led to a further 

 specialisation of the pallial formation, resulting in the birth 

 of the neopallium — a cortical area where all the sensory impulses 

 brought to the cerebral hemispheres along these new channels 

 might be received, be blended in consciousness with those 

 coming from other sense-organs, and leave impressions which 

 might be stored, as it were, in this neopallium, and so influence 

 other sensations and states of consciousness at some subsequent 

 time. The neopallium is thus the organ of associative 

 memory." And he also states that " the first appearance of 

 a definite neopallium coincides with the transformation of 

 the skin over the whole surface of the body into a highly 

 specialised tactile organ." This conclusion may even be carried 

 still further, as Friedenthal ^ has pointed out, to explain the 

 great development of the brain which is obvious even in the 

 earliest human skulls. Thus, by man becoming naked, owing 

 to the hair being reduced to a minimum, the skin became 

 more than ever before the seat of the reception of tactile im- 

 pressions, and thereby the extent of the neopallium became 

 increased, and the mentality of the human race correspondingly 

 enlarged. 



The theory of the evolution of limbs in the Vertebrata 

 from continuous; fin-folds (extending along the entire length 

 of the body), which is now so generally accepted, furnishes 

 another instance of the general principle of this paper. The 

 paired fins as well as the unpaired fins appear first of all 

 as longitudinal folds of the body-wall, converging towards 

 the anus ; in the Elasmobranch embryo each somite gives 



' Some Problems relating to the Evolution of the Brain. Arris and Gale 

 Lectures, Roy. Coll. of Surgeons, 1909. 



* Beitr. zur Nah(rgeschichie des Menscheii. Jena, 1908. 



